Radiation sensitive self-assembled monolayers and uses thereof

ABSTRACT

The invention is directed to a radiation sensitive compound comprising a surface binding group proximate to one end of the compound for attachment to a substrate, and a metal binding group proximate to an opposite end of the compound. The metal binding group is not radiation sensitive. The radiation sensitive compound also includes a body portion disposed between the surface binding group and the metal binding group, and a radiation sensitive group positioned in the body portion or adjacent to the metal binding group. The surface binding group is capable of attaching to a substrate selected from a metal, a metal oxide, or a semiconductor material.

GOVERNMENT RIGHTS

The U.S. government may have rights in this invention due to fundingfrom the Defense Advanced Research Projects Agency (DARPA) underContract N66001-00-C-8083.

FIELD OF THE INVENTION

The invention relates to multi-functional compounds used to formmolecular assemblies and the use of the molecular assemblies asthin-film resists in lithographic applications.

BACKGROUND OF THE INVENTION

The fabrication of small patterned features with a desired functionalityis important in a wide variety of fields and applications. Improvementsin lithographic techniques to decrease image dimensions have allowed themicroelectronics industry to fabricate denser and fastermicroelectronics chips. Traditional resist technology, however, israpidly reaching the limits of achievable dimension reductions.Consistent production of sub-60 nm linewidths will require advancesbeyond the current approaches.

As the size of microelectronic devices shrink, it becomes necessary todefine ever smaller features—current manufacturing lines produce sub 70nm features. Resolving features in this size range requires the use of193 or 157 nm optical exposures, or electron beam (e-beam) radiation andvery thin resist films. Traditional resist films contained phenolicresins that had a moderate resistance to “dry” transfer methods such asreactive ion etching (RIE). Due to the high absorbance of phenolicmoieties at wavelengths below 200 nm, resists for deep UV exposure mustbe primarily aliphatic or cycloaliphatic. The aliphatic polymers used asresist films in the deep UV regime are less etch resistant thantraditional phenolic resins. To achieve high resolution, the aspectratio of the resist thickness to the width of the features must be keptcomparable, so it may not be possible to increase the thickness of theresist to compensate for its poorer etch performance.

In addition, the use of high numerical aperture lenses to increase theresolution of optical exposures is reducing the depth of focus of thetools, which also pushes towards the use of very thin resist films.Another problem that occurs when creating fine lithographic features iscollapse of resist lines. Even for relatively thin resists (0.1-0.3 um)the wet development step often causes line collapse due to surfacetension effects of the aqueous developers and rinses on features withhigh aspect ratios (Jung, M-H, et al., Proceedings SPIE, Vol. 5039,1298, 2003).

Line edge roughness is another significant concern in the sub-100 nmfeature regime. Traditional resists are composed of polymer chains with“protected” side groups that can react with acids. Photoacid generatorsproduce acids when exposed to light, which then diffuse in the film andcatalyze the deprotection of the polymer chain, allowing it to becomesoluble in the basic developer. The roughness of lithographic featuresdefined by this process can be related to both the size of the polymerchains dissolving out of the film and by the diffusion length of thephotoacids (Yoshimura, T., et al., Japan. J. Appl. Phys., Vol. 32, 6065,1993). For features in the sub-100 nm regime, both of these sources ofline edge roughness are important.

Self-assembled monolayers (SAMs). It is well known that organicmolecules containing certain terminal head groups will self assemblefrom solution to form monolayers on specific surfaces (Ulman, A., AnIntroduction to Ultrathin Organic Films, Academic Press, Chap. 3, 1991).The most common monolayers are formed from organic thiols which attachto gold substrates, organic alkoxy or chloro silanes which react withsilicon dioxide, or phosphonic acids, hydroxamic acids, or carboxylicacids which react with metal oxides (Taylor, C. et al., Langmuir, Vol.19, 2665, 2003). The monolayers are stabilized by the chemisorption ofthe head group to the surface and the formation of covalent bonds (inthe case of silanes or thiols) or ionic bonding (in the case of acids)of the terminal head group with the surface, as well as intermolecularinteractions between the molecules such as van der Waals forces, pi-piinteractions or hydrogen bonding.

Self-assembled monolayers are prepared by placing substrates in asolution containing from 0.1 mM to about 1% of the molecules forming themonolayer in a non-reactive, low boiling solvent. The self-assemblyprocess may take from a few minutes up to a day or more to formcomplete, dense monolayers (Ulman, A., An Introduction to UltrathinOrganic Films, Academic Press, Chap. 3, 1991).

There are various examples of monolayers with terminal tail groups thatcan bind to metal ions or metal complexes, including phosphonic acidswhich bind to Zr or Hf (Fang, M., et al., J. Am. Chem. Soc., Vol. 119,12184, 1997), pyridine which binds to metals or metal complexes such asRh complexes (Lin, C. et al., J. Am. Chem. Soc., Vol. 125, 336, 2003) orZr complexes (Hatzor, A. et al., Langmuir, Vol. 16, 4420, 2000), orterpyridine which is capable of binding to a variety of metal ions(Hofmeier, H., et al., Chem. Soc. Rev., Vol. 33, 373, 2004; Maskus, M.,et al., Langmuir, Vol. 12, 4455, 1996) The metal/monolayer complexeswill self assemble in solution through the chelation of the metalions/complexes by the tail group of the monolayer.

The initial metal/monolayer complexes may in some cases be extended intomultilayer structures through the use of difunctional “linking ligands”,such as diphosphonic acids, dipyridines, diisocyanides orditerpyridines. By sequential exposure to the linking ligand and themetal species, layers may be built up on the original monolayer/metalcomplex. Films with at least 30 ligand/metal bilayers have beenassembled in this fashion (Lin, C. et al., J. Am. Chem. Soc., Vol. 125,336, 2003).

The concept of using monolayers as ultrathin resists had been proposedand explored by others. Long chain alkyl thiols or silanes have beenpatterned using UV light or e-beam radiation (Smith, R., et. al., Prog.Surf. Sci., Vol. 75, 1, 2004; Ryan, D., et. al., Langmuir, Vol. 20,9080, 2004; Zharnikov, M., et. al., J. Vac. Sci. Technol. B, Vol. 20,1793, 2002; Calvert, J. Vac. Sci. Technol. B, Vol. 11, 2155, 1993).However, the monolayer films that have been proposed to date do not havesufficient RIE etch resistance to transfer images using standard dryetching techniques.

SUMMARY OF THE INVENTION

The invention is directed to a radiation sensitive compound comprising asurface binding group proximate to one end of the compound forattachment to a substrate, and a metal binding group proximate to anopposite end of the compound. The metal binding group is not radiationsensitive. The radiation sensitive compound also includes a body portiondisposed between the surface binding group and the metal binding group,and a radiation sensitive group positioned in the body portion oradjacent to the metal binding group. The surface binding group iscapable of attaching to a substrate selected from a metal, a metaloxide, or a semiconductor material.

In one embodiment, the invention is directed to a radiation sensitivecompound of formula ISB-BP-MB-RS  I

wherein SB is a surface binding group; BP is a body portion; MB is ametal binding group; and RS is a radiation sensitive group. Theradiation sensitive group is displaced from the metal binding group uponexposure to UV or e-beam radiation, thereby activating the metal bindinggroup to interact with a metal species.

In another embodiment, the invention is directed to a radiationsensitive compound of formula IISB-RSBP-MB  II

wherein SB is a surface binding group; MB is a metal binding group; andRSBP is a body portion that includes a radiation sensitive group. Uponexposure to UV or e-beam radiation the metal binding group is displacedfrom the compound. The radiation sensitive group in the body portion isnot an amine.

The invention is also directed to a lithographic process for patterninga substrate comprising: providing a substrate and attaching a pluralityof radiation sensitive compounds to the substrate, wherein the radiationsensitive compounds include a surface binding group for attachment tothe substrate and a metal binding group; exposing the surface attachedradiation sensitive compounds to UV or e-beam radiation; and complexingthe metal binding group of the radiation sensitive compounds with ametal species selected from a metal cation, metal compound, or metal ormetal-oxide nanoparticle to form metallized radiation sensitivecompounds in a predetermined pattern on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present invention will become apparentupon consideration of the following description of the invention whenread in conjunction with the drawings, in which:

FIG. 1( a)-1(g) is a schematic representation of a process of theinvention related to the forming of a “positive tone” resist film;

FIG. 2( a)-2(g) is a schematic representation of a process of theinvention related to the forming of a “negative tone” resist film.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to radiation sensitive compoundscomprising: a surface binding group proximate to one end of the compoundfor attachment to a substrate; a metal binding group proximate to anopposite end of the compound (NOTE: it may not be at the opposite end ofthe molecule if the radiation sensitive group is the terminal group); abody portion disposed between the surface binding and the metal bindinggroups; and a radiation sensitive group positioned in the body portionor adjacent to the metal binding group. The body portion provides asufficient intermolecular interaction with neighboring moleculesattached to the substrate to form a monolayer on the substrate. Theradiation sensitive group controls the ability of the monolayer tocoordinate metals, either by cleaving the metal binding group from themonolayer upon irradiation in the case of “positive tone” monolayers, orby cleaving from the metal binding group and allowing it to coordinatemetals in the case of “negative tone” monolayers. Also, the metalbinding group of the radiation sensitive compounds are not radiationsensitive.

The term “radiation sensitive” refers to the breakage of covalentchemical bonds in a particular position of the compound upon exposure toultraviolet (UV) or electron beam (e-beam) radiation under lithographicconditions. A metal binding group is not radiation sensitive if themetal binding group attached to the body portion of the compound retainsthe capability of interacting with a metal species following exposure toUV or e-beam radiation. A metal binding group that is activated towardsmetal species interactions by displacement of a radiation sensitivegroup adjacent to the metal binding group is not itself radiationsensitive. An amine group is one example of a radiation sensitive metalbinding group.

The radiation sensitive compounds can function as negative or positivethin-film resists for use in lithography depending upon the position ofthe radiation sensitive group in the compound. In particular, theradiation sensitive compounds are designed for high resolution (sub-100nm) lithography that utilizes UV and e-beam radiation.

In one embodiment, the exposure of the radiation sensitive group toradiation results in the cleaving of the metal binding group from thebody portion of the compound. Consequently, the exposed compound can nolonger bind metals, and thereby functions as a positive tone resist.

In another embodiment, the exposure of the radiation sensitive group toradiation results in the cleaving of the radiation sensitive group fromthe compound at a position adjacent to the metal binding group, andthereby activates the metal binding group to complex with a metalspecies. Consequently, the metal binding group of the exposed molecularprecursor is activated toward metallization, thereby functioning as anegative tone resist.

It is to be understood that one of ordinary skill in the art can designany number of radiation sensitive compounds with each compound having asurface binding group, a metal binding group, a body portion and aradiation sensitive group. In one embodiment, the invention is directedto a radiation sensitive compound of formula ISB-BP-MB-RS  I

SB is a surface binding group, BP is a body portion, MB is a metalbinding group and RS is a radiation sensitive group. The radiationsensitive group is displaced from the metal binding group upon exposureto UV or e-beam radiation, thereby activating the metal binding group tointeract with a metal species.

In another embodiment, the invention is directed to a radiationsensitive compound of formula IISB-RSBP-MB  II

Again, SB is a surface binding group and MB is a metal binding group.However, the radiation sensitive group is positioned in the body portionof the compound and identified as RSBP. The radiation sensitive group inthe body portion is not an amine. In this case, the radiation sensitivegroup can cause cleavage of the metal binding group from the compoundupon exposure to UV or e-beam radiation.

Examples of surface binding groups that can be incorporated into thecompounds for interacting with or binding to a particular substratesurface with chemical specificity include one or more of the functionalgroups selected from a phosphine, phosphonic acid, carboxylic acid,thiol, epoxide, amine, imine, hydroxamic acid, phosphine oxide,phosphite, phosphate, phosphazine, phosphonic acid, azide, hydrazine,sulfonic acid, sulfide, disulfide, aldehyde, ketone, resorsinol, silane,germane, arsine, nitrile, isocyanide, isocyanate, thiocyanate,isothiocyanate, amide, alcohol, selenol, nitro, boronic acid, ether,thioether, carbamate, thiocarbamate, dithiocarbamate, dithlocarboxylate,xanthate, thioxanthate, alkylthiophosphate, dialkyldithiophosphate orany combination thereof.

Some of the more preferred surface binding groups include:

a. thiols that bind to metal and semiconductor surfaces (e.g. Au, Pd,Pt, AuPd, Si, Ge, GaAs, Cu);

b. Selenols that bind to a similar group of metals and semiconductors asthiols

c. isocyanides that bind to metal surfaces;

d. phosphonic acids, hydroxamic acids, carboxylic acids, suflonic acidsor resorsinols that to bind to metal oxide surfaces (e.g. aluminumoxides, zirconium oxides and hafnium oxides);

e. hydroxamic or carboxylic acids—which bind to metals and metal oxides

f. chloro and alkoxy silanes that bind to silicon oxide surfaces; and

g. dienes alcohols, and aldehydes that bind to silicon surfaces.

Examples of metal binding groups that can be incorporated into thecompounds include:

a. nitrogen heterocycles such as pyridine, dipyridine or terpyridine.These sigma donating nitrogen ligands can bind to a variety of metals atdifferent oxidation states across the periodic table such as those ofGroup IV (Ti, Zr and Hf), Group V (Nb and Ta), Group V (Cr, Mo and W),Group VI (Mn and Re) and Group VIII metals (Fe, Co, Ni, Ru, Rh, Pd, Os,Ir and Pt);

b. phosphonic acids that selectively bind to metal ions including Zr andHf;

c. sulfonic acids that selectively bind to metal ions including Fe; and

d. isocyanides that selectively bind to Group VIII metals as well assome early transition metals.

Examples of radiation sensitive groups that can be incorporated into thecompounds include:

a. nitrobenzyl groups;

b. benzyl ether groups;

c. succinimidyl sulfonic acid groups; and

d. alkyl thiols or disulfides.

Compounds A, B, C and D are some examples of radiation sensitivecompounds of the invention, and thus, compounds that can be used inphotolithography to pattern a substrate. Each of the compounds have asurface binding group (SB); A, Si(OCH₃)₃; B, PO(OH)₂; C, thiol; and D,hydroxamic acid. Each of the compounds have a metal binding group (MB);A, PO(OH)₂; B, pyridine; C, terpyridine; and D, S(O)₂OH. Each of thecompounds have a radiation sensitive group (RS); A, nitrobenzyl; B,benzyl ether; C, carbon-sulfur bond; and D, succinimidyl. Compounds Band C have radiation sensitive groups positioned in the body portion,and therefore, the metal binding group is displaced upon exposure of thecompounds to radiation. Compounds A and D have radiation sensitivegroups adjacent to the metal binding group, and therefore, the metalbinding group is activated upon exposure. Again, compounds A to D areonly exemplary, and thus, the invention is not restricted to these fourcompounds. For example, a particular radiation sensitive compound can bedesigned according to the device application and the type of radiationused for exposure.

The radiation sensitive compounds can be used to provide ultra-thin(monolayer or multilayer) self-assembled films that can be patterned bystandard lithographic exposure techniques such as e-beam or deep UVoptical exposure systems. The radiation sensitive compounds of theinvention are designed to form self-assembled films, and thenselectively complex with metal species, e.g., metal ions or metalnanoparticles, that will improve the etch resistance of the films inplasma or reactive ion etching environments. Patterned images can thenbe transferred into oxide, metal, semiconductor, or hardmask layersbeneath the self-assembled films.

FIG. 1( a) is a schematic representation depicting the radiationsensitive compounds in the form of an assembled monolayer on asubstrate. As shown, the radiation sensitive compounds include a surfacebinding group 10 attached to the substrate 13, a metal binding group 11and a radiation sensitive group 12 positioned in the body portion. FIG.1( b) depicts the exposing of the monolayer of FIG. 1( a) with UVradiation 14 through an opening in mask 15 or by patterned e-beamradiation which does not require the use of a mask. FIG. 1( c) depictsthe developed pattern following exposure. As shown, the radiationsensitive portion of the compounds exposed to the radiation have beendisplaced in-part from the monolayer leaving a predetermined pattern.Depending upon the radiation sensitive moiety, those compounds exposedcan form small molecule residues that will either vaporize or can berinsed from the surface by common solvents. The surface of the monolayernow contains regions with and without terminal metal bindingcapabilities. The monolayer is then contacted with a metal species 16,e.g., metal ions and the metal species will complex with the metalbinding groups of the unexposed compounds, FIG. 1( d).

In some applications, one can rely on the metal film of the patternedmonolayer to pattern the substrate. However, for many other applicationsthe monolayer is insufficient, and a thicker film is needed with agreater density of metal species in the film. The build-up of themonolayer can continue by contacting the complexed metal species with aconnecting ligand 17, FIG. 1( e). The process of contacting theconnecting ligand with metal species and the complexed metal specieswith a subsequent connecting ligand can proceed any number of timesuntil the desired thickness of the film and density of metal species issufficient to provide a certain degree of etch selectivity, FIG. 1( f).Once the desired film thickness is obtained, the exposed portions of thesubstrate 13 can be etched resulting in a patterned substrate, FIG. 1(g).

FIG. 2( a) is a schematic representation depicting the radiationsensitive compounds in the form of an assembled monolayer on asubstrate. As shown, the radiation sensitive compounds include a surfacebinding group 10 attached to the substrate 13, a metal binding group 11and a radiation sensitive group 12 adjacent to the metal binding group.The body portion of the radiation sensitive compounds that make up themonolayer is not shown, but it is disposed between the surface bindinggroup 10 and the metal binding group 11. FIG. 2( b) depicts the exposingof the monolayer of FIG. 2( a) with UV or e-beam radiation 14 through anopening in mask 15 or through the use of patterned e-beam radiation.FIG. 2( c) depicts the developed monolayer following exposure. As shown,the radiation sensitive groups exposed to the radiation have beendisplaced from the metal binding groups in the monolayer leaving apredetermined pattern. The exposed portion of the monolayer is nowavailable to complex with a metal species 16, e.g., metal ions, as themetal binding groups of the compounds have been activated towardcomplexation, FIG. 1( d).

In some applications, one can rely on the metal film of the patternedmonolayer to pattern the substrate. However, for many other applicationsthe monolayer is insufficient, and a thicker film is needed with agreater density of metal species in the film. The build-up of themonolayer can continue by contacting the complexed metal species with aconnecting ligand 17, FIG. 2( e). The process of contacting theconnecting ligand with metal species and the complexed metal specieswith a subsequent connecting ligand can proceed any number of timesuntil the desired thickness of the film and density of metal species issufficient to provide a certain degree of etch selectivity, FIG. 2( f).Once the desired film thickness is obtained, the unexposed portions ofthe substrate 13 can be etched resulting in a patterned substrate, FIG.2( g).

As described, the monolayer comprising the radiation sensitive compoundscan provide the foundation upon which subsequent layers containingvarious metal species can be constructed. These subsequent layers areconstructed using connecting ligands and subsequent attachment of themetal species. The radiation sensitivity of the assembled monolayerallows lithographic definition of regions of the substrate wherelayer-by-layer structures may or may not be fabricated. Theincorporation of metal species into the ultra-thin resist layerincreases its resistance to dry (reactive ion) etching techniques. Theinvention uses these metal-organic layers to create patterned featureson surfaces that are of potential importance to a wide range of fieldsincluding silicon technology, carbon nanotube fabrication,nanoelectronics, electroless plating, sensors, biotechnology, andnon-linear optics.

Some of the process advantages of the invention include:

1. the use of ultra-thin resist films will minimize the impact of areduced depth of focus for many of the high energy optical exposuresystems;

2. the use of ultra-thin resist films will minimize line collapse offine features, which can result from surface tension effects on thickresist images;

3. the minimization of line edge roughness through the use of individualradiation sensitive compounds rather than large polymeric molecules andphotoacid generators that can diffuse outside the exposed region;

4. to provide a site selective patterned substrate for applications suchas carbon nanotube (CNT) and nanowire growth or electroless plating,fabrication of field effect transistor (FET) device componentsincluding, but not limited to, contact or gate structures; and

5. to provide device structures for chemical or biological sensors, andnon-linear optics.

In addition to use in traditional lithographic applications, the abilityto selectively localize metal atoms on a range of surfaces may be usefulin a wide range of applications. A technique that allows site specificdeposition of selected metal ions or nanoparticles would permitmolecules or supramolecular structures to be formed specifically wherethey are needed. This invention may allow the synthesis of nanotubes ornanowires at the site of use by patterning the required metal catalystallowing nanotubes/wires to only form is specified areas, as describedin U.S. patent application entitled “Spatially selective growth ofcarbon nanotubes and semiconductor nanowires using molecularassemblies”, and assigned to International Business MachinesCorporation.

The process of the invention can also be used to lithographically definevery fine metal containing features where the metal acts as the seedlayer or catalyst for electroless plating. It combines the resist andseed layers into one ultra-thin layer with the potential for very highresolution.

The patterned organic/metal assembly layers of the invention can be usedin the fabrication of nanoscale FET or memory devices. The electricalproperties of such devices can be controlled through the choice of theorganic layer and metal species, e.g., select metal ions. Charge storagebehavior, potentially useful in memory devices, has been demonstratedusing iron/terpyridine complexes (Li, C., et al., J. Am. Chem. Soc.,Vol. 126, 7750, 2004). Layer-by-layer organic/metal structures have alsodisplayed non-linear optical properties (Katz, H. et al., Science, Vol.254, 1485, 1991) as well as electrochemical and electrogeneratedchemiluminescence (Guo, A., et al. Anal. Chem., Vol. 76, 184, 2004). Theprocess of the invention allows lithographic definition of features withthe specified functionality directly on the substrate of interest.

A monolayer comprising the radiation sensitive compounds of theinvention can be formed by exposing an appropriate substrate to a dilutesolution containing the compounds. For example, the substrate can be atop insulating layer such as an oxide or a top metal (metal alloy) layerdeposited on another material such as silicon. Base metal, metal alloyand semiconductor substrates (Si, SiGe, GaAs) can also be used. Typicalsolutions contain 1 mM to 1% of the radiation sensitive compound in anon-interacting, low boiling solvent, and typical immersion times rangefrom 20 minutes to overnight. An assembled radiation sensitive monolayerwith a terminal metal binding group is depicted in FIG. 1( a), and onewith a terminal radiation sensitive group is depicted in FIG. 2( a).

The metal species that can be used to complex with the metal bindinggroups include metal ions, metal complexes, or metal nanoparticles. Thesubstrate containing the patterned monolayer with the terminal metalbinding groups is placed in contact with a dilute solution of theappropriate metal species. The metals will tend to assemble on the metalbinding groups, as depicted in FIGS. 1( d) and 2(d). Exemplary metalspecies include solutions of metal halides in alcohol or aqueoussolutions, metal/organic complexes such as di-rhodium complexes intoluene solutions, or metal nanoparticles stabilized withalkylcarboxylic acids in solution in hexane or other nonpolar solvents.

As described, once the assembled monolayer includes the complexed metalspecies additional layers can be constructed on the monolayer using aconnecting ligand. Again, the metal terminated assembly is placed incontact with solutions containing the connecting ligands to producelayered assemblies like those depicted in FIGS. 1( e) and 2(e).Exemplary connecting ligands include diterpyridines such astetra-2-pyridinylpyrazine, dipyridines, such as dipyridinyl ethylene, ordi-phosphonic, sulfonic, or carboxylic acids. Typical ligandconcentrations will be between 0.1-10 mM in appropriate solvents. Theassembly of layer-by-layer structures can be constructed by alternatecontact of the assembly layer(s) to metal-containing solutions andconnecting ligand containing solutions until the film has attained thedesired thickness.

Layer-by-layer films containing a significant content of metals may thenbe used as a barrier for dry or wet etching of the substrate, asdepicted in FIGS. 2 g and 3 g. The etch resistance of the film may alsobe increased through the use of aromatic organic or highly fluorinatedorganic molecules as the linking ligands. It is also possible to growpatterned layer-by-layer films on thin, sacrificial etch barriers, suchas hardmasks, initially transferring the image into the hardmask andusing the patterned hardmask to transfer the image into the underlyingstructure.

The invention herein disclosed reduces or eliminates several problemswith current lithographic resists for creating sub-100 nm features. Theultra-thin radiation sensitive monolayers (˜10 to 20 Å) allow thepossibility of true “top surface” imaging to optimize resolution andalleviate issues with depth of focus of advanced optical exposuresystems. The films will not be subject to absorption concerns faced bythicker resist films in the deep UV. Due to their thickness and theaspect ratio of the features, these will not be subject to the surfacetension effects which lead to collapse in thicker films. Edge roughnessshould also be minimized due to the use of individual radiationsensitive molecules rather than larger polymer chains with multiplereactive sites and photoacid generators that diffuse through the film.

A wide range of additional applications of the materials defined in thisinvention are also possible. Some of these applications may not requirean extended or multilayer assembly structure. Films that are justprepared through step d) in FIG. 1 or 2 will have patterned regionscontaining a uniform layer of metal atoms. The appropriate selection ofmetal species can also be used as the seed or catalytic layer forpatterned electroless plating. The plated features defined by thisprocess could have much smaller dimensions than those formed throughconventional lithographic definition of catalytic layers. Patternedmetal containing regions could also be used as the catalyst for thesite-specific synthesis of organic molecules for applications inmolecular recognition such as the selective binding of biomolecules orin the creation chemical sensors. The patterning capabilities ofmetal/catalyst containing molecules described herein would allow for thefabrication of dense sensor arrays.

EXAMPLE 1

Mercaptophenylterpyridine (MPTP) which contains thiol, surface bindinggroups and terpyridine, metal binding groups was prepared (Auditore, A,et. al, Chem. Comm. 2494, 2003). An assembled monolayer comprising MPTPwas prepared by immersing O₂ plasma cleaned gold substrates into a 1 mMsolution of MPTP in 3:1 toluene:ethanol overnight. The presence of theMPTP monolayer was confirmed by both UV and FTIR spectroscopy.

The monolayer of MPTP was then exposed to 1-10 mM solutions of variousmetal halides in alcohol or water for 10 minutes including RuCl₃, IrBr₃,RhCl₃, TiCl₃, SnCl₄, ZrCl₄, WCl₄, and Cucl₂. Again, spectroscopicevidence (UV and FTIR) indicated the complexation of the metal ions tothe MPTP. The substrates were then immersed in a 1 mM solution oftetra-2-pyridylpyrazine, a connecting ligand, in 1:1 ethanol:toluenesolution for 10 minutes. The substrates were then cycled betweenimmersion in the metal halide and the connecting ligand solutions toconstruct assembled multilayered films. The UV spectra of the films wererecorded after each immersion and demonstrated relatively linearincreases in absorbance consistent with uniform layered growth. In somecases, an assembled film with up to 20 bilayers of metal ions andconnecting ligand were prepared. AFM measurements also indicatedincreasing film thicknesses that were consistent with the film thicknesspredicted from molecular modeling.

EXAMPLE 2

A monolayer of MPTP was exposed to 193 nm UV light (7.5 J/cm²) and noresidual absorbance in either UV or FTIR scans was observed, thusindicating complete reaction of the sulfur-carbon bond and removal ofthe portion of the molecule containing terpyridine. The exposedmonolayer was also cycled through the solutions of metal halide andconnecting ligand, and these did not demonstrate the increase inabsorbance and film thickness as did the unexposed substrates of Example1.

EXAMPLE 3

4-[N-(3-triethoxysilyl)propyl]-carbamoyl-2-nitrobenzyl isonicotinate(TCNI) which binds to silicon dioxide through the ethoxysilyl groups,and has a pyridine metal binding group and a nitrobenzyl radiationsensitive group was prepared according to the synthetic procedurerepresented in Scheme 2. 4-Bromomethyl-3-nitrobenzoic acid (A) wasrefluxed overnight with sodium carbonate in acetone/water (1:1). Aftercooling to room temperature, the reaction mixture was made acidic with 1N hydrochloric acid and the product was extracted into ethyl acetate,dried over magnesium sulfate and rotary evaporated to yield4-hydroxymethyl-3-nitrobenzoic acid. The 4-hydroxymethyl-3-nitrobenzoicacid (B) was dissolved in pyridine and reacted with isonicotinoylchloride hydrochloride at room temperature for 2 days. The resultantsolution was poured onto ice, stirred overnight at room temperature andextracted with ethyl acetate. The organics were dried over magnesiumsulfate and rotary evaporated to remove the solvents. Residual pyridinewas removed by the addition of toluene followed by rotary evaporation.The resultant solid was slurried in ethanol at room temperature and theproduct, 4-carboxy-2-nitrobenzyl isonicotinate, was isolated byfiltration and dried under vacuum.

The 4-carboxy-2-nitrobenzyl isonicotinate (C) was treated with excessthionyl chloride and a few drops of dimethylformamide at roomtemperature for 45 minutes, followed by rotary evaporation to removethionyl chloride and azeotropic removal of thionyl chloride by 3additions of toluene followed by rotary evaporation to give4-chlorocarbonyl-2-nitrobenzyl isonicotinate hydrochloride (D). The4-chlorocarbonyl-2-nitrobenzyl isonicotinate hydrochloride (D) andexcess triethylamine were dissolved in chloroform and cooled in anice/acetone bath. A chloroform solution of 3-aminopropyltriethoxysilanewas added dropwise and the reaction was allowed to warm to roomtemperature and stirred for 4 hours. The solvents were removed by rotaryevaporation. The resultant mixture was treated with ether and filteredto remove salts. The filtrate was rotary evaporated and purified byflash chromatography on silica gel using ethyl acetate as the eluent toyield 4-[N-(3-triethoxysilyl)propyl]carbamoyl-2-nitrobenzylisonicotinate.

Monolayers of TCNI were prepared by immersing O₂ RIE cleaned siliconchips with 5000 Å of thermal oxide into a 1 mM solution of TCNI in drytoluene overnight. Upon removal from the solution the chips were rinsedin clean solvent and baked at 120 C for 10 minutes. Ten layers of metalions and connecting ligands were built up on top of a TCNI monolayer asdescribed in Example 1. Samples with Ru³⁺, Rh³⁺, and Ir³⁺ were prepared.All samples, along with uncoated control chips, were etched in a RIEtool using CHF₃ and O₂ at a pressure of 50 mTorr and a power of 150watts for 3.5 minutes.

The etch was designed to completely remove the film such that themaximum resistance of the film to RIE could be determined by thedecrease in the loss of SiO₂ relative to the control samples. The chipswith ten layers of Ir³⁺ lost an average of 750 Å less oxide, the Ru³⁺layers lost an average of 500 Å less oxide, and the Rh³⁺ lost 380 Å lessoxide than the control samples. The predicted film thickness for a 10layer film is about 90 Å, so all of the LBL films demonstrate etchresistances far greater than 1:1 (which is typical for organic resistfilms).

1. A lithographic process for patterning a substrate comprising:providing a substrate and attaching a plurality of radiation sensitivecompounds to the substrate, wherein the radiation sensitive compoundsinclude a surface binding group for attachment to the substrate and ametal binding group; exposing the surface attached radiation sensitivecompounds to e-beam radiation; complexing the metal binding group of theradiation sensitive compounds with a metal species selected from a metalcation, metal compound, or metal or metal-oxide nanoparticle to formmetalized radiation sensitive compounds in a predetermined pattern onthe substrate; attaching a connecting ligand to the metalized radiationsensitive compounds followed by complexing a second metal species to theconnecting ligand and transferring the pattern to the underlyingsubstrate by dry etching wherein the plurality of radiation sensitivecompounds comprises; a surface binding group proximate to one end of thecompound for attachment to a substrate; a metal binding group proximateto an opposite end of the compound, wherein the metal binding group isnot radiation sensitive; a body portion disposed between the surfacebinding group and the metal binding group; and a radiation sensitivegroup positioned in the body portion or adjacent to the metal bindinggroup and wherein the surface binding group is a thiol and the radiationsensitive group is a nitrobenzyl group.